It seems like these lesions are of Seborrheic dermatitis
,which is a chronic relapsing and harmless condition of the skin. The exact cause is unknown but its believed that the skin becomes more sensitive to a yeast called Malassezia
,which prefer moist and warm areas of the body.
I would suggest to wash them with Nizoral
AD shampoo three times a week and apply Hydrozole cream twice a day for 7-10 days.
IF you think they respended to the medications then its most probably SD,but if not then i am afraid you need to see a doctor so that he can have a look live at them for you and proceed further.
thanks and all the best.